The invention relates to a belt tensioner for seat belt systems in vehicles, especially an end fitting tensioner, comprising a belt shaft housing as well as a belt shaft being pivoted about an axis in the belt shaft housing.
Belt tensioners for seat belt systems are generally known already from automotive engineering. In so-called end fitting tensioners in the case of activation of the belt tensioner the actually fixed end of a webbing usually connected to the seat frame or the vehicle body is tightened in order to provide for tensioning of the entire webbing. In the state of the art both linearly operating as well as rotatory end fitting tensioners are described. In the rotatory end fitting tensioner the webbing end is connected to a belt shaft which is driven upon activation of the belt tensioner so as to wind webbing onto the belt shaft.
The generic DE 10 2006 018 455 A1 for example describes an end fitting tensioner consisting of a belt retractor receiving the end of the seat belt and of a tensioning device connected thereto for the belt shaft of the belt retractor. The belt shaft is accommodated in the belt shaft housing in a rotatable and radially movable manner. Due to the radial play the belt shaft can take a locked position in which the belt shaft is retained to be rotationally fixed relative to the belt shaft housing in the webbing extension direction, a release position in which the belt shaft is rotatable relative to the belt shaft housing in both directions, or any intermediate position. The belt shaft is radially moved to its locked position only by the force acting in the webbing extension direction upon rotation thereof, in which locked position an interlock configuration of the belt shaft interacts with a blocking toothing of the belt shaft housing.
The play of the belt shaft in the belt shaft housing present in the radial direction and in the circumferential direction can entail undesired noise development during driving operation. Moreover, in cases of restraint without activation of the belt tensioner rotation and/or radial displacement of the belt shaft relative to the belt shaft housing and thus an undesired release of belt webbing may occur.